1. Field of the Invention
This invention relates generally to magnetic media, and, more particularly, to a magnetic disk with separate park and take-off zones.
2. Description of the Related Art
Magnetic media, such as rigid or hard disks, are well known for storing data in magnetizable form. The disks are typically rotated by an electric motor on a central axis while data transducing heads positioned in close proximity to a recording surface of the disk record and/or read data. The transducing heads, during normal reading and recording operations, are maintained at a preselected distance from the recording surface, flying over the disk on a bearing of air as the disk rotates. The transducing heads commonly come into contact with the recording surface of the disk in a number of typical circumstances: such as when the disk is stationery; when the disk accelerates from a stopped orientation; and during deceleration just before the disk comes to a stop. Each type of contact is problematic, producing distinctive, undesirable performance issues.
A phenomenon commonly known as stiction has been observed in circumstances where the disk has been stationary for an extended period of time with the transducing heads resting thereon. Stiction is the result of a number of circumstances, including the highly polished and smooth nature of the recording surfaces of the disk and the transducing head, as well as a build-up of lubrication on the transducing head. These factors combine to cause the transducing head to adhere to the disk such that the torque of the motor used to rotate the disk cannot overcome the adhesion, and the disk will not rotate. Thus, the disk cannot begin to rotate, much less attain a rotational velocity sufficient to fly the transducing head over the disk. Moreover, even if the stiction is insufficient to prevent the disk from rotating, it will still substantially contribute to a mechanical wearing of the recording surface of the disk, eventually corrupting or causing a loss of data stored thereon.
The prior art has attempted to solve this problem by identifying an area of the disk that is exclusively used as a "parking" and "take-off" zone for the transducing head. Commonly, as is described in U.S. Pat. No. 5,062,021, this "take-off" and "parking" zone has been intentionally roughened to reduce stiction. A roughness on the order of 1 microinch has been observed to produce a desirable reduction in instances of stiction. A roughening of the disk surface, however, necessitates an increased flying height to reduce instances of contact between the disk and the transducing heads. Unfortunately, increased flying height has a dramatic negative impact on the density at which data can be stored on the disk. Storage density decreases exponentially with increased flying height. This flying height problem is particularly exacerbated as state-of-the-art disk drives approach flying heights on the same order as the desired roughness of the take-off and parking zones. That is, as flying heights approach 1 microinch, increased contacts and with the media attendant damage will only become more problematic.
Additionally, the "parking" and "take-off" zone of a magnetic disk can also be damaged by what is commonly referred to as "head slap." When the disk is stopped with the transducing heads located in the "parking" zone and in contact with the surface of the disk, it sometimes occurs that the disk drive is suddenly and violently accelerated, such as by dropping, bumping, kicking, etc. This acceleration can cause the transducing head to momentarily lift-off of the disk and then be slammed onto the surface of the disk, producing a dent with raised edges. In extreme cases, the raised edges approach 5 microinches, towering above a desirable 1 microinch roughening. Thus, when the disk is being accelerated to operating speeds (or decelerating from operating speeds) with the transducing head located in the "parking" and "take-off" zone, numerous violent contacts with the transducing head occur. These violent contacts are obviously undesirable, contributing to premature wear and failure of the transducing heads.
Furthermore, a roughened "parking" and "take-off" zone produces air flow characteristics that will not fly the transducing head at the desired height until the speed of the disk attains a large percentage of its final speed. That is, when the disk surface is roughened, the transducing head will spend more time over the "parking" and "take-off" zone at a height below that of the desired flying height. Moreover, there is a direct relationship between the degree of roughness and the disk speed needed to achieve the desired flying height. Accordingly, a transducing head will take longer to attain a desired flying height over a disk having a roughness on the order of 1 microinch as compared to a disk having a roughness on the order of 0.5 microinch. It should be appreciated that the more time it takes for a transducing head to reach the proper flying height, the more contacts that are likely to occur with the disk, and, accordingly, the more damage that will be done to the head and the disk.
The present invention is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above.